The first time you use the Activity app on your Apple Watch, you’re asked to provide personal details such as gender, age, height and weight. This information helps your wrist gadget, to properly determine important metrics like the distance you run, how far you walk, the amount of calories burned and other data used by the Workout and Activity apps.

Your smartwatch works, by default, with average formulas which determine the length of your stride, depending on your Height and Gender. Your Weight contributes to accurate calorie burning results, while Age is taken in consideration when new Activity goals are suggested. In conclusion, the above mentioned personal info is enough for correct results. However, you can take this one step further and eliminate even the slightest errors from your Watch’s metrics.

Calibrate Apple Watch Accelerometer
Use the GPS, available on the paired iPhone, to gain extra distance accuracy measurement on the Apple Watch. The Cupertino-base company states that you need around 20 minutes of running or walking, tracked both by the Workout app on your wrist gadget and your iPhone’s GPS. This allows your Watch to compare its estimated distance measurements, to the real ones handed by the Global Positioning System. Furthermore, watch OS will then adjust your real stride metrics, by dividing the total distance measured by the GPS, to the number of streps recorded by the Watch’s accelerometer.

How To Calibrate With iPhone GPS1. Grab both Apple devices and go to a flat outdoor area. Avoid woods or other similar terrain where GPS signal could be shielded by the surroundings.2. On your iOS device open Settings -> Privacy. Make sure that Location Services are ON.3. Continue to browse the same settings for Privacy -> Location Services -> System Services and check if Motion Calibration & Distance feature is enabled.4. Raise your wrist, navigate to the Workout app on your Watch and pick Outdoor Run or Outdoor Walk.5. Start running or walking holding your iPhone in your arm or attaching it to your body with the help of an armband or wristband. Keep it up for 20 minutes.

Walking vs Running
Once calibrated your smartwatch will store the new data for your stride and use it to provide metrics with the same precision, even when the iPhone isn’t around. Do mind, that you’ll lose the calibration records if you unpair the Apple Watch from your iPhone. For optimal results, calibrate your Apple Watch’s accelerometer while walking, jogging or running in separate sessions. It offers individualized stride length info, which helps your Watch to easier determine when, you’re running or brisk walking. This leads to improved calorie burning calculation and impacts the whole range of fitness metrics.

Tip: You can split the above mentioned 20 minutes of calibration, in several sessions and still improve accuracy, as long as you perform the same type of activity!

Update Your Physical Info
Whenever your personal information changes, adjust your data on the Apple Watch, to maintain fitness metrics precision. Grab your iPhone and open the Apple Watch app. Browse to My Watch -> Health and edit the fields that have changed: adjust your Weight if you lost a few pounds, or your Height if you’re still in your teens and grow taller.